Tree Mortality Following Boreal Forest Fires Reveals Scale-Dependant Interactions Between Community Structure and Fire Intensity |
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Authors: | Benjamin D Dalziel Ajith H Perera |
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Institution: | (1) Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA;(2) Ontario Forest Research Institute, Sault Ste. Marie, Ontario, Canada |
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Abstract: | Fire disturbance patterns influence forest communities at a range of spatial scales. Forest community structure may also influence
fire disturbance patterns, because tree species vary in their fuel value and in their tolerance to fire damage. However, the
influence of community structure on fire disturbance likely depends on latent ecological differences between fires and on
the spatial scale at which patterns are observed. Using data on fire intensity, community structure, and post-fire tree survival
in four systematically sampled boreal forest fires, we tested the hypotheses that: (1) patterns in post-fire tree survival
reflect interactions between fire intensity and community structure; (2) these relationships change with the spatial scale
of observation. To test the first hypothesis, we used information theoretic methods to compare eight generalized linear mixed
effects models describing the influence of community structure and fire intensity on tree survival in a 500 m2 sample plot, accounting for latent fire-to-fire differences in response. To test the scaling hypothesis, we reaveraged the
data at nine successively larger spatial resolutions up to approximately 2 km2, at each resolution tracking the parameter values of the best model. When fit to the plot-level data, the dominant feature
of the best model was a strong intensity–survival correlation which varied from fire to fire, and depended on plot-level community
structure. In some fires, community structure and survival became more tightly coupled at larger scales, whereas fire intensity
became less important. These results support the view that fire disturbance patterns are influenced by cross-scale interactions
between community structure and fire intensity. |
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